I read in another group page that you need to resubmit all the documents to do the renewal and it is as troublesome as a new application as compared to doing a border run (a night stay recommended). If you are in Phuket, maybe a night in Malaysia's Penang or KL will be easier.
I just received my DTV, it took 10 days. Applied online in Singapore. One of the additional information I was asked to send in was the last 3 months' bank statements (Nov, Dec and a screenshot of latest update). I remembered it was stated online the 500k baht must be in your account for 60 days.